### National Information Center on Health Services Research and Health Care Technology (NICHSR)

 Glossary
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Term Definition
Prevalence The occurrence of a condition in a population expressed usually as the rate or proportion of the population that exhibits that condition.
Probability sample A sample drawn from a defined population in a way that allows inferences from the sample to the larger population with a known probability of statistical uncertainty or error.
Public health threat A threat to the health of a population that results from risks from behavior, infection, habits or social circumstances.
Public Use files Files prepared for the use of groups, researchers or any interested member of the public who are NOT members of the research team that collected the data. Usually, steps are taken to mask the identities of subjects or respondents so as to protect their privacy.
Reliability of data Consistency of data reports from one time to the next. Data are reliable if the same observations lead to the same reported indicators at different times and under different conditions.
Risky behavior Behavior that puts health status into risk by using tobacco, excessive use of alcohol, accident prone driving, inactivity or obesity.
Sampling error Uncertainty due to collecting data from a sample rather than every member of a population.
Statistical estimate A result based on a statistical procedure. Statistical estimates are characterized by their precision and accuracy. They exhibit uncertainty due to the methods used to collect, compile and report results.
Sampling theory The rigorous methods created to define how to collect a sample from a population in a way that allows valid inferences from the sample to the population.
Statistical precision The degree to which estimates are exact. In sampling, this is influenced by the number of cases observed and the procedures used to draw the sample as well as the methods used to analyze the data.
Statistical representativeness The degree to which inferences from a sample reflect conditions in a population. Representativeness is influenced by the procedures used as well as assumptions about the extent of variation in the population.
Statistical summary An indication of the trend or overall conditions based on observed indicators.
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